Phonology
The reconstruction of Proto-Semitic (PS) was originally based primarily on the Arabic language, whose phonology and morphology (particularly in Classical Arabic) is extremely conservative, and which preserves as contrastive 28 out of the evident 29 consonantal phonemes. Thus, the phonemic inventory of reconstructed Proto-Semitic is very similar to that of Arabic, with only one phoneme less in Arabic than in reconstructed Proto-Semitic. As such, Proto-Semitic is generally reconstructed as having the following phonemes (as usually transcribed in Semitology):
Read more about this topic: Proto-Semitic Language